Which of the following is true about risks associated with exposure of the embryo and fetus in utero? 

A. Exposure in the preimplantation phase usually results in permanent growth retardation. 

B. Exposure in utero has not been considered to provide a risk for carcinogenesis to the fetus. 

C. Exposure in utero results in a period of high risk for mental retardation at 15-25 weeks of gestation and lower risk at 8-15 weeks of gestation. 

D. Exposure in utero results in microcephaly especially before 15 weeks of gestation. 

E. Exposure of the fetus in utero has not been associated with changes in school performance or IQ.